DESCRIPTION (Taken from application) Children with extrahepatic biliary atresia (EHBA) represent the largest group of pediatric patients requiring liver transplantation. To date, a cause for the majority of cases of EHBA remains unknown. A viral etiology has been suspected and several viral agents, particularly reovirus type 3, have been seen as potentially related. Previous work from our laboratories implicating group A rotavirus in the induction of biliary obstruction in mice, led to the testing of liver samples from human infants with EHBA for the presence of rotavirus RNA. We employed the polymerase chain reaction (PCR) and while we were unable to detect group A rotavirus, we did detect group C rotavirus in EHBA patients and not in controls. The overall objective of the present proposal is to investigate possible viral etiologies of EHBA with particular emphasis on group C rotavirus. Our specific aims are to determine the nature of the virus(s) detected by sequencing the PCR products, of group C rotavirus, and, if detected, group A rotavirus, reovirus type 3 and cytomegalovirus (CMV). The gravity of the prognosis for infants with extrahepatic biliary atresia dictates that everything be done to establish an etiology in order to find ways of treating the affected infants and preventing the occurrence of the disease. Fulfilling the goals of this proposal will be a step in that direction.